blabbersnitch

Thanks, that was a helpful introduction. Just what I needed.

when it is time to install, you are asked n or Y. Don't type 'y' or 'yes', you have to type it exactly as shown: as an upper case Y, otherwise it aborts (some linux programming nerd had a bit of righteous fun with that one!)

This is good project for a number of reasons in a number of areas. Well done.Common valves (or tubes) are made for operation at hundreds of volts and their published characteristics never show their behaviour at low voltages. However, they can work at low voltages (I built a guitar effects pedal with one that runs at 12V). A test circuit that can quicky plot the low voltage characteristics of the valves would be great! Your circuit with a little development could do that. Common valves (12AX7s, 12AU7s) operate much like n-channel mosfets. But they are more like depletion mode mosfets. I think your circuit would only work with enhancement mode mosfets (am I right?). Maybe your next revision could feature a socket for some triodes with negaive gate/grid voltage capability!

A 40A Fotek solid state relay for a few bucks? I don't think so. That is a counterfeit unit. It is no surprise that the triac inside is underrated.

I did a lot of customising, probably too much to put here in the comments section of Mach_5's instructable. But I am happy to share, so send me a personal message and I will get back to you that way.

Yes. I used this and it worked (for the benefit of others reading this). The webpage is slightly dated (the options presented were slightly different to what I saw). I chose the manual options (option 4), then:PiTFT screen: 2.2 - 3.2 resistive (option #2)HDMI rotation: landscape (option #1)Display orientation: 90 degrees (option #2)

You can get the audio from the out of the RPi Zero. I used this guide at Adafruit:https://learn.adafruit.com/adding-basic-audio-ouput-to-raspberry-pi-zero?view=allIt describes how to assign the audio PWM outputs to GPIO pins that are present on the Zero. Read from ‘Changing GPIO ALTS’I changed pins 32 & 33 (GPIO12 & 13) to ALT0 mode, which reassigned them to PWM audio outputs. There is a handy ground connection at pin 34. I suggest you also install their WiringPi/gpio software as it provides a way to see what your inputs/outputs are doing. Once I had the PWM outputs at pins 32 & 33, I summed them into a filter and fed that into a small amplifier. I used one similar to this:https://www.adafruit.com/product/2130and fed that into a speaker from I pulled from a broken …

You can get the audio from the out of the RPi Zero. I used this guide at Adafruit:https://learn.adafruit.com/adding-basic-audio-ouput-to-raspberry-pi-zero?view=allIt describes how to assign the audio PWM outputs to GPIO pins that are present on the Zero. Read from ‘Changing GPIO ALTS’I changed pins 32 & 33 (GPIO12 & 13) to ALT0 mode, which reassigned them to PWM audio outputs. There is a handy ground connection at pin 34. I suggest you also install their WiringPi/gpio software as it provides a way to see what your inputs/outputs are doing. Once I had the PWM outputs at pins 32 & 33, I summed them into a filter and fed that into a small amplifier. I used one similar to this:https://www.adafruit.com/product/2130and fed that into a speaker from I pulled from a broken kids’ toy. I didn’t test as suggested at Adafruit, I just played a game and enjoyed the sweet 80’s arcade music coming from it :-)

I hate to be a critic after the great effort you have made and the trouble you have gone to post your Instructable, but hopefully these criticisms will be constructive.The 1k input resistor to the opamp is effectively in parallel with the 220ohm resistor across the CT (as the 1k resistor goes to a virtual ground). It means your effective burden is about 180ohm, not the 220ohm you might think it is. This isn’t a big deal really, but will effect calculations if not considered. Canging your inverting opamp configuration to a non-inverting opamp configuration would get rid of this issue.And as someone mentioned, a bleed resistor across the output cap would be a good idea.And also as mentioned, you are really only measuring peak. The relationship between peak and rms will vary from equip…

I hate to be a critic after the great effort you have made and the trouble you have gone to post your Instructable, but hopefully these criticisms will be constructive.The 1k input resistor to the opamp is effectively in parallel with the 220ohm resistor across the CT (as the 1k resistor goes to a virtual ground). It means your effective burden is about 180ohm, not the 220ohm you might think it is. This isn’t a big deal really, but will effect calculations if not considered. Canging your inverting opamp configuration to a non-inverting opamp configuration would get rid of this issue.And as someone mentioned, a bleed resistor across the output cap would be a good idea.And also as mentioned, you are really only measuring peak. The relationship between peak and rms will vary from equipment to equipment. Even with the mathematical approach you have taken to accurately measure a test current, as soon as you try to measure a non-linear load, your results will be out. You also have a non-linearity introduced by the rectifying diode (its effect on the result varies with input current, but at low levels, you won’t be generating enough voltage to even force it to conduct).If you take the AC voltage straight to the Arduino (suitably offset), maybe you could do a true RMS calculation?

I love this! I made it as a present for a friend, with the writing on top like yours.

Unfortunately, when you use your stamp, the 'J' will be backwards. I realised this part way through my design. You can use 'mirror' in the CREATE menu to fix it.

I didn't have any wax, so I melted one of my son's crayons.

Don't forget to mirror your design (if it matters)!